JPH1184109A - Lenticular lens sheet and transmission screen - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To make it possible to increase the thickness and to increase the BS ratio even if the pitch remains fine. SOLUTION: A light incident lens 11 formed on the light incident side and having a substantially elliptical cross section, and an output lens 1 formed on the light condensing portion of the incident lens 11 on the light output side and having a concave lens cross section.
2 was provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LCD and a DMD.
The present invention relates to a lenticular lens sheet and a transmission screen suitable for projecting and observing an image from an image light source having a cell structure such as a (Digtal Micro-mirror Device).

[0002]

2. Description of the Related Art Conventionally, a rear projection type television using three CRTs of red, green and blue as an image light source and a transmission screen as a screen has been known. The transmissive screen includes a Fresnel lens sheet that converts the light projected from the CRT into substantially parallel light, and a diffusion sheet that diffuses light over a wide range.

[0003] As a light diffusion sheet, a lens element such as a lenticular lens for condensing light on the light incident side is formed, and the vicinity of the focal point of the lens element is defined as a light exit surface. A lenticular lens sheet with a black stripe (BS) is used in which a light absorbing layer is provided to diffuse light and reduce the influence of external light.

As an image light source, a projection television using an LCD or DMD has been developed. In a projection television using an LCD or DMD, a lattice pattern caused by a cell structure of a panel is projected on a transmission screen, and an image is projected on a lenticular lens sheet having a periodic structure at a constant pitch as described above. When observed, moire may occur due to the sampling effect of the lenticular lens. In order to prevent the occurrence of such moiré, it is preferable to reduce the pitch of the lenticular lens so as to be 1 / 3.5 or less of the projected grating pattern.

Further, in a projection television using an LCD or DMD, a glare of an image called scintillation occurs. However, reducing the pitch of the lenticular lens is effective in weakening the scintillation.

On the other hand, a transmissive screen using a lenticular lens sheet with a BS diffuses light over a wide range of 40 ° or more, and at the same time, when forming a BS, the distance between the light incident lens and the light exit surface is reduced. It must be less than about 1.3 times the lens pitch. In this case, in order to make the moire between the lattice pattern projected on the transmissive screen and the lens pitch inconspicuous, the lens pitch is
The thickness must be 0.4 mm or less, and the thickness of the lens must be 0.52 mm or less.

[0007]

However, when the thickness of the above-mentioned conventional transmission screen is reduced, rigidity is reduced, and it is difficult to hold the screen flat. Also,
It is very difficult to accurately form such a thin lens sheet by extrusion or the like.

Further, at present, the LCD light source is not so powerful and has a poor contrast as compared with a light source using three CRTs of red, green and blue which have been conventionally used. As a transmissive screen for LCD, a screen having a higher contrast than that of a conventional CRT is desired. Here, in the case of a lenticular lens having a light absorbing layer on the observation side, the most effective method of improving the contrast is to increase the BS ratio because the light source is a single tube.

[0009] It is an object of the present invention to provide a lenticular lens sheet and a transmissive screen which can be made thicker and have a higher BS ratio even if the pitch is still fine.

[0010]

According to a first aspect of the present invention, there is provided a light incident side lens section (11) formed on a light incident side and having a substantially elliptical cross section. A lenticular lens sheet comprising: a light-emitting side lens section (12) formed in the light-collecting section of the incident side lens section and having a concave lens cross section. According to a second aspect of the present invention, the light incident side lens portion (1) is formed on the light incident side and has a substantially elliptical cross section.
1) and an emission-side lens portion (1) formed on the light-collecting portion of the incidence-side lens portion on the light emission side and having a concave lens-shaped cross section.
2) and a lenticular lens sheet provided with a light absorbing layer (14) formed on a non-light-collecting portion of the light-entering lens portion.

[0011] The invention of claim 3 is claim 1 or claim 2.
In the lenticular lens sheet described in 1, the relationship between the lenticular pitch p and the lens thickness t is 1.3 ≦ t /
A lenticular lens sheet, wherein p ≦ 1.9.

According to a fourth aspect of the present invention, there is provided the first to third aspects.
2. The lenticular lens sheet according to claim 1, wherein the converging coefficient k of the incident side lens portion (11) satisfies −0.35 ≦ k ≦ −0.1. is there.

According to a fifth aspect of the present invention, there is provided the first to fourth aspects.
In the lenticular lens sheet according to any one of the above, a substantially trapezoidal convex portion (13) formed on the non-light-collecting portion on the light emission side, and a light absorbing layer (1) formed on the convex portion.
4) A lenticular lens sheet comprising:

According to a sixth aspect of the present invention, in the lenticular lens sheet according to the fifth aspect, the light absorbing layer (1) is provided.
The lenticular lens sheet 4) is also formed on the trapezoidal inclined surface (13a) of the convex portion.

According to a seventh aspect of the present invention, in the lenticular lens sheet according to the fifth aspect, the convex portion (13) is provided.
Is a layer (1) containing no light diffusing agent on at least its surface.
6) A lenticular lens sheet comprising:

[0016] The invention of claim 8 is the invention of claims 1 to 7.
In the lenticular lens sheet according to any one of the above, the light absorbing layer has a ratio (BS ratio) of 60%.
A lenticular lens sheet characterized by the above.

According to a ninth aspect of the present invention, in a transmission screen used for a rear projection type television, a Fresnel lens sheet (20) for converting at least projection light into substantially parallel light.
Disposed on the light exit side of the Fresnel lens sheet,
An image is formed by diffusing projection light.
A lenticular lens sheet (10) according to any one of the above items.

According to a tenth aspect of the present invention, in the transmission screen according to the ninth aspect, the Fresnel lens sheet (20) has a light diffusing element (21).

[0019]

Embodiments of the present invention will be described below in more detail with reference to the drawings. (First Embodiment of Lenticular Lens Sheet) FIG.
FIG. 2 is a view schematically showing a lenticular lens sheet according to a first embodiment of the present invention. The lenticular lens sheet 10 </ b> A of this embodiment includes a light incident lens 11,
The light output lens 12, the convex portion 13, the light absorbing layer 14 and the like are provided.

This lenticular lens sheet 10 is
The circle, ellipse, aspherical surface, and the like are used for the shape of the light incident lens 11. The light incident lens 11 is designed so that the light converging point is located inside the sheet.
Is a concave lens shape. For this reason, the thickness with respect to the pitch of the screen can be increased to 1.9 times as much as 1.1 to 1.3 times the normal value. At this time, the light emitting lens 12 may appropriately use a concave circle, a concave ellipse, a concave hyperbola, a concave parabola, or the like as its cross-sectional shape.

FIG. 3 is a diagram showing an optical path of image light of the lenticular lens sheet according to the first embodiment. When the light exit lens 12 has a concave shape, the shape of the light entrance lens 11 is determined by setting the cone coefficient k in the following equation 1 to −0.35 ≦ k.
≦ −0.1, preferably −0.3 ≦ k ≦ −0.2.

[0022]

(Equation 1)

In this case, the light A near the center forms a converging point near the light exit lens 12 as shown in FIG. A condensing point is formed inside, and refracted further outward by the light exit lens 12 (B1 in FIG. 3).

FIG. 4 is a diagram showing the relationship between the horizontal half-value angle (αH) and the gain of the lenticular lens sheet according to this embodiment. In the lenticular lens sheet 10A of the first embodiment, αH is suppressed to about 30 °, and the center gain and the gain of 50 ° or more are emphasized. As shown in FIG. 4, when k is smaller than −0.35, αH increases, but a cutoff occurs at about 40 °, and the central gain decreases as αH increases. When k is -0.1 or more, αH is not more than 20 °, which is not preferable.

According to the first embodiment, since the light emitting lens 12 has a concave lens shape, the thickness with respect to the screen pitch can be increased. Therefore, it is possible to reduce the occurrence of moiré while maintaining the mechanical strength.

(Second Embodiment of Lenticular Lens Sheet) FIG. 5 is a view showing a second embodiment of a lenticular lens sheet according to the present invention. In each of the embodiments described below, portions that perform the same functions as in the first embodiment described above are denoted by the same reference numerals, and redundant description will be omitted as appropriate.

At present, the LCD light source is not so powerful as compared with the CRT light source, and the contrast is poor. Therefore, the transmission type screen for the LCD does not sacrifice the light source light more than the CRT light source. Is required to be increased. Here, the most effective method for improving the contrast is to increase the BS ratio because the light source is a single tube. However, when the light emitting lens 12 is formed in a concave shape and the projection light is condensed inside, if the BS 14 is formed in a substantially rectangular convex portion as in the related art, the emitted light is applied to the convex portion of the BS. There is a problem.

In the lenticular lens sheet 10B of the second embodiment, the convex portion 13B is formed in a substantially trapezoidal shape, and a light absorbing agent is applied to the slope 13a to form a light absorbing layer 14B. Outgoing light is projected portion 13
B can be prevented, and the BS rate can be increased. In the second embodiment, glass beads,
A diffusion layer 15 for diffusing the projected light is formed by mixing acrylic beads or the like as a diffusing agent.

According to the second embodiment, since the substantially trapezoidal convex portion 13 is provided and the light absorbing layer 14 is provided on the convex portion 13, the emitted light is not kicked. In addition, since the light absorption layer 14 was also formed on the trapezoidal inclined portion 13a of the convex portion 13, B
The S rate can be increased.

(Third Embodiment of Lenticular Lens Sheet) FIG. 6 is a view showing a third embodiment of a lenticular lens sheet according to the present invention. In the substantially trapezoidal convex portion 13B of the second embodiment, if the light diffusing agent comes out to the inclined portion 13a, there is a possibility that a portion where the light absorbing agent is applied and a portion where the light absorbing agent is not applied may occur. The appearance is unfavorable due to the appearance of roughness.

In view of this, the lenticular lens sheet 10C according to the third embodiment is configured so that the diffusing agent does not protrude to at least the inclined portion 13a of the convex portion 13B so that roughness is not generated. As a specific method, a non-diffusion layer 16 containing no diffusing agent is formed on the entire observation side. According to the third embodiment, since the non-diffusion layer 16 is provided, the surface has no roughness.

(Embodiment of Transmission Screen) FIG.
FIG. 2 is a view showing an embodiment of a transmission screen according to the present invention. The transmission screen of this embodiment includes a Fresnel lens sheet 20 and a lenticular lens sheet 10 (10A, 10B, 10C, etc.) disposed on the observation side thereof.
And

In a projection television using an LCD or DMD, an image glare called scintillation occurs. Usually, to reduce scintillation,
As described in JP-A-8-313865, the portion where the light diffusing agent is mixed is divided into two or more portions. Therefore, in the present embodiment, the base material 2 of the Fresnel lens sheet 20 is used.
1, a predetermined amount of a diffusing agent is mixed. Here, as the Fresnel lens, a circular Fresnel lens or a linear Fresnel lens with the lens surface facing the observation side can be suitably used.

In the case of the lenticular lens sheet having the shape of this embodiment, as shown by the incident light C in FIG. 7, the horizontal diffusion characteristics are further expanded by the diffusing agent mixed in the base material 21 of the Fresnel lens sheet 20. Can be. And scintillation can be reduced.

[0035]

The present invention will be described below in more detail with reference to specific examples. Impact resistant acrylic resin (refractive index 1.5
Using 1), a lenticular lens sheet was formed by extrusion. At this time, acrylic beads having an average particle diameter of 30 μm (refractive index: 1.49) and an average particle diameter of 17 μm
The glass beads (refractive index: 1.535) were mixed at a ratio of 6: 1 as a diffusing agent and mixed into a lenticular lens sheet.

Here, the following three types of lenticular lens sheets 10A, 10B and 10C were prepared, and
To Example 3. (Example 1) Example 1 is a lenticular lens sheet 10A formed into a single layer by extrusion molding.
The height of S14 is set to 0.08 mm (5 °) (FIG. 1).
reference). In the lenticular lens sheet 10A, the pitch p = 0.36 and the lens thickness t = 0.67, so that t / p９1.9. The cone coefficient k of the light incident lens 11 is -0.1.

Example 2 In Example 2, a lenticular lens sheet 10 formed into two layers by extrusion molding.
B, 70% of the surface is BS14, and the height of BS14 is 0.06 mm (50 °) (see FIG. 5). Since the lenticular lens sheet 10B has a pitch p = 0.35 and a lens thickness t = 0.54,
t / p ≒ 1.5. The cone coefficient k of the light incident lens 11 is -0.3.

Example 3 In Example 3, a lenticular lens sheet 10 formed in three layers by extrusion molding.
C, the diffusion layer 15 and the non-diffusion layer 16 are formed, and the height of the BS 14 is set to 0.06 mm (50 °) (see FIG. 6). This lenticular lens sheet 10
C is t / p ≒ 1.5 since the pitch p = 0.35 and the lens thickness t = 0.54. Also, the light incident lens 1
The conic coefficient k of 1 is -0.3.

On the other hand, a Fresnel lens sheet 20 was formed by a UV manufacturing method using a base material 21 prepared by mixing 2.0 parts by weight of the acrylic beads with the impact-resistant acrylic resin (thickness: 2.5 mm).

Table 1 shows the measurement results of the light diffusion characteristics of the combination of the Fresnel lens sheet 20 and the lenticular lens sheets 10A, 10B, and 10C using a micro-deviation luminance meter.

[0041]

[Table 1]

In Table 1, the upper row shows the lenticular lens sheets 10A, 10B, and 10C alone, and the lower row shows a combination of them and the Fresnel lens sheet 20. The shape of the light incident lens 11 represents a conical coefficient k.

In Example 1, a bump was formed almost vertically (5 °), and only the upper portion was coated with a light absorbing agent. The BS rate is
40%. In Examples 2 and 3, the bulge of BS14 is 5
It was formed at 0 °, and the light absorbing agent was also applied to the inclined portion. The BS ratio was 65%. While the appearance was rough in Example 2, Examples 1 and 3 were good without roughness.

The light output shape of 0.2R means that the cross-sectional shape is a part (arc) of a circle having a radius of 0.2 mm, and a minus sign indicates a plus of a convex circle of a normal lenticular lens. Therefore, the concave circle is represented by a minus sign. The luminance angle in Table 1 is the same as αH described above, and the 輝 度 luminance angle is the angle at which the gain becomes の of the center gain (gain of 0 °) in FIG. For example, “25” in the first embodiment is
This indicates that the half luminance angle (αH) is 25 °.

In Example 1, in combination with the Fresnel lens sheet, the half luminance angle (αH) was close to 30 °, and in Examples 2 and 3, the conventional pitch was 0.7.
ΑH is 35 as in the above lenticular lens sheet.
゜ We were able to secure. Further, in Examples 2 and 3, the same as in a normal lenticular lens sheet, 50
゜ A close 1/10 luminance angle could be secured.

In a lenticular lens having a pitch of 0.35 mm, in the conventional design, the plate thickness had to be reduced to about 0.45 mm or less. However, in the case of acrylic resin, this thickness has a rigidity. In addition, it was easy to crack, and was difficult to manufacture.

In the first embodiment, the value of c in Expression 1 is
It is 0.212, and in Examples 2 and 3, it is 0.1764.
The values of p / 2c are 0.85 (Example 1) and 0.
99 (Examples 2 and 3). When this value is large, the plate thickness must be reduced, and when it is small, the diffusion angle cannot be obtained. That is, about 0.8 to 1.0 is the applicable range.

[0048]

As described above, according to the present invention,
Since the light exit side lens portion is a concave lens, the thickness of the lenticular lens sheet can be increased. Further, since the light absorbing layer is provided on the substantially trapezoidal convex portion, the BS ratio can be increased.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of a lenticular lens sheet according to the present invention.

FIG. 2 is an enlarged view showing a first embodiment of a lenticular lens sheet according to the present invention.

FIG. 3 is a diagram illustrating an optical path of image light of a lenticular lens sheet according to a second embodiment.

FIG. 4 is a diagram showing a relationship between a horizontal half-value angle (αH) and a gain of the lenticular lens sheet according to the embodiment.

FIG. 5 is a view showing a second embodiment of the lenticular lens sheet according to the present invention.

FIG. 6 is a view showing a third embodiment of the lenticular lens sheet according to the present invention.

FIG. 7 is a view showing an embodiment of a transmission screen according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lenticular lens sheet 11 Light entrance lens 12 Light exit lens 13 Convex part 14 Light absorption layer 15 Diffusion layer 16 Non-diffusion layer 20 Fresnel lens sheet 21 Base material

Claims (10)

[Claims] 1. An incident side lens section formed on a light incident side and having a substantially elliptical cross section and a condensing section of the incident side lens section on a light exit side and having a concave lens section. Lenticular lens sheet provided with a lens unit. 2. A light-incident side lens section formed on the light incident side and having a substantially elliptical cross section, and an output side formed on a light condensing section of the incident side lens section on the light output side and having a concave lens cross section. A lenticular lens sheet, comprising: a lens portion; and a light absorbing layer formed on a non-light-collecting portion of the light incident lens portion. 3. The lenticular lens sheet according to claim 1, wherein the relationship between the lenticular pitch p and the lens thickness t is 1.3.
Lenticular lens sheet, wherein ≦ t / p ≦ 1.9. 4. The lenticular lens sheet according to claim 1, wherein a conical coefficient k of the incident side lens portion is −0.35 ≦.
A lenticular lens sheet, wherein k ≦ −0.1. 5. The lenticular lens sheet according to claim 1, wherein the convex portion has a substantially trapezoidal shape formed in a non-light-collecting portion on a light emitting side. And a light absorbing layer formed on the lenticular lens sheet. 6. The lenticular lens sheet according to claim 5, wherein the light absorbing layer is also formed on a trapezoidal inclined surface of the convex portion. 7. The lenticular lens sheet according to claim 5, wherein the convex portion has a layer containing no light diffusing agent on at least the surface thereof. 8. The lenticular lens sheet according to claim 1, wherein a ratio (BS ratio) of the light absorbing layer is 60% or more. Sheet. 9. A transmissive screen used in a rear projection television, wherein a Fresnel lens sheet for converting at least projected light into substantially parallel light, and a light emitting side of the Fresnel lens sheet. A transmission screen, comprising: the lenticular lens sheet according to any one of items 8 to 8. 10. The transmission screen according to claim 9, wherein the Fresnel lens sheet has a light diffusing element.